nyan = "nyanpass"
N = int(input())
gre = [list(input().split()) for i in range(N)]
renchon = set()
for j in range(N):
    cnt = 0
    for i in range(N):
        if i == j:
            continue
        if gre[i][j] == nyan:
            cnt += 1
    if cnt == N - 1:
        renchon.add(j + 1)
if len(renchon) == 1:
    for ans in renchon:
        print(ans)
else:
    print(-1)